Instagram is clarifying its rules around sexual, illegal and other inappropriate content, including posts involving revenge porn.

The site now expressly forbids users from threatening to post intimate images of others, as well as sexual content involving minors, the service said in its updated policies on Thursday. More broadly, photos showing sexual intercourse, genitals, and close-ups of fully-nude buttocks aren’t allowed, Instagram says.

For safety reasons, Instagram may also remove images that show nude or partially nude children, the company said.

Instagram previously had a ban on nude images and other content like photos depicting extreme violence or gore. But as the Facebook-owned company has grown, it’s now clarifying its rules, aiming to keep its app friendly for a general audience. Instagram, which Facebook bought for US$1 billion in 2012, now has more than 300 million users who log in monthly.

In the process, Instagram is sure to encounter some of the same policing issues Facebook has: how best to let its users freely express themselves while also restricting what the site deems to be offensive, illegal or inappropriate content. Making those determinations is not always easy.

“Even when this content is shared with good intentions, it could be used by others in unanticipated ways,” Instagram said in reference to its rules around nude photos of children.

Photos of post-mastectomy scarring and breast-feeding are OK, Instagram said, as is nudity in photos of paintings and sculptures. Facebook, however, has generated controversy in multiple instances of censoring or removing photos of art containing nudity.

Also, Instagram posts offering sexual services, buying or selling illegal or prescription drugs, as well as promoting recreational drug use are not allowed, the updated rules state. Instagram’s rules around posts promoting the sale of regulated goods like firearms, however, are more nuanced.

Posts supporting or praising terrorism, organized crime or hate groups are not allowed, Instagram said in its clarified rules.

Instagram’s ability to enforce its policies will depend partly on the extent to which users flag the content. Instagram has built-in reporting tools to report such posts.

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